LTN says he did. He says Bon teachings are older than Vasu, which is how Vasu could get something from them. If that is not true, it calls into question the validity of Bon history.
Not Bon methodology. History.
However, if it is true, then that is very interesting, because it opens up the possibility for Buddhist history to be much more diverse than is generally held today.
Your talking about a history from an age that is completely ending. That history doesn't matter much anymore. It all just gets lumped into old ways that wont exist soon.
As a side note, I think what you are picking up on is my disdain for one aspect of Abhidharma, that it has been ascribed to Buddha, when, in fact, monks made it up. I find it very weird and hypocritical that there was this huge lie made by folks with vows not to lie. I find it strange and troubling that this practice of making up lies and calling them Buddha's teachings is something diffused within all Buddhist schools. Again, this is a side note.
I am pretty sure the various chapters of the Abhidharma were taught by Arhats. The Theravada sect claim their Abhidhamma was taught by the Buddha, and it probably was in pure visions.
Where the credibility has been tainted once, trust is difficult to maintain. The upshot is that one can still penetrate this manifold opacity and uncover the true gems of liberation.